Added the possibilty to not only make quadratic items

internal/model/configuration.go

@@ -33,6 +33,9 @@ type LayoutPreview struct {
 	CellHeightMM   float64          `json:"cell_height_mm"`
 	FootprintWMM   float64          `json:"footprint_width_mm"`
 	FootprintHMM   float64          `json:"footprint_height_mm"`
+	TrimOffsetMM   float64          `json:"trim_offset_mm"`
+	CanvasWidthMM  float64          `json:"canvas_width_mm"`
+	CanvasHeightMM float64          `json:"canvas_height_mm"`
 	Columns        int              `json:"columns"`
 	Rows           int              `json:"rows"`
 	Count          int              `json:"count"`

internal/model/item.go

@@ -1,13 +1,74 @@
 package model
 
-import "time"
+import (
+	"fmt"
+	"math"
+	"time"
+)
 
 // ItemSpec holds mask parameters (from template CLI).
 type ItemSpec struct {
-	SizeMM    float64 `json:"size_mm"`
-	BleedMM   float64 `json:"bleed_mm"`
-	MarginMM  float64 `json:"margin_mm"`
-	PaddingMM float64 `json:"padding_mm"`
+	// SizeMM is legacy: square product when width_mm/height_mm are unset.
+	SizeMM         float64 `json:"size_mm,omitempty"`
+	WidthMM        float64 `json:"width_mm,omitempty"`
+	HeightMM       float64 `json:"height_mm,omitempty"`
+	CornerRadiusMM float64 `json:"corner_radius_mm,omitempty"`
+	BleedMM        float64 `json:"bleed_mm"`
+	MarginMM       float64 `json:"margin_mm"`
+	PaddingMM      float64 `json:"padding_mm"`
+}
+
+// ViewportWidth returns the SVG viewport width used for layout packing.
+func (s ItemSpec) ViewportWidth() float64 {
+	if s.WidthMM > 0 {
+		return s.WidthMM
+	}
+	return s.SizeMM
+}
+
+// ViewportHeight returns the SVG viewport height used for layout packing.
+func (s ItemSpec) ViewportHeight() float64 {
+	if s.HeightMM > 0 {
+		return s.HeightMM
+	}
+	return s.SizeMM
+}
+
+// markLengthMM is crop-mark extension outside the product (must match svgtemplate).
+const markLengthMM = 6
+
+// TrimOffsetMM is bleed + margin + crop marks drawn outside the product rect.
+func (s ItemSpec) TrimOffsetMM() float64 {
+	return s.BleedMM + s.MarginMM + markLengthMM
+}
+
+// CanvasWidthMM is the full item SVG width including trim and crop marks.
+func (s ItemSpec) CanvasWidthMM() float64 {
+	return s.ViewportWidth() + 2*s.TrimOffsetMM()
+}
+
+// CanvasHeightMM is the full item SVG height including trim and crop marks.
+func (s ItemSpec) CanvasHeightMM() float64 {
+	return s.ViewportHeight() + 2*s.TrimOffsetMM()
+}
+
+// Normalize fills width/height from legacy size_mm and validates dimensions.
+func (s *ItemSpec) Normalize() error {
+	if s.WidthMM <= 0 && s.HeightMM <= 0 && s.SizeMM > 0 {
+		s.WidthMM = s.SizeMM
+		s.HeightMM = s.SizeMM
+	}
+	if s.WidthMM <= 0 || s.HeightMM <= 0 {
+		return fmt.Errorf("width_mm and height_mm must be positive")
+	}
+	if s.CornerRadiusMM < 0 {
+		return fmt.Errorf("corner_radius_mm must be non-negative")
+	}
+	maxR := math.Min(s.WidthMM, s.HeightMM) / 2
+	if s.CornerRadiusMM > maxR {
+		return fmt.Errorf("corner_radius_mm must be at most %.2f", maxR)
+	}
+	return nil
 }
 
 // Item is a printable product type (SVG mask) placed on a plate.